[AIE2P] Add SingletonCopyEdges dag mutator in pre-scheduler #469
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
khallouh
requested review from
abhinay-anubola,
abnikant,
andcarminati,
F-Stuckmann,
gbossu,
katerynamuts,
konstantinschwarz,
martien-de-jong,
niwinanto,
SagarMaheshwari99 and
stephenneuendorffer
as code owners
| continue; | ||
|
|
||
| auto MO = MI.getOperand(1); | ||
| if (!(MO.isReg() && MO.getReg().isPhysical())) |
There was a problem hiding this comment.
nit:
if (!MO.isReg() || !MO.getReg().isPhysical())
continue;
| if (!MBB->isLiveIn(PhysReg)) | ||
| continue; | ||
|
|
||
| SDep SingletonCopyEdge(&SU, SDep::Artificial); |
There was a problem hiding this comment.
What about moving this into the scope of the if below?
|
|
||
| for (SUnit &SU2 : DAG->SUnits) { | ||
| MachineInstr &MI = *SU2.getInstr(); | ||
|
|
There was a problem hiding this comment.
Are we creating an Edge from SU to itself?
|
Can we have a test that runs only premisched? |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Some instructions take a singleton register class in their operands. If a copy of that same physical register from the function arguments is moved closer to its user by the pre-scheduler and it happens to move past an instruction requiring that singleton register class, a live range interference is created which the register allocator cannot resolve by evicting the function argument physical register, leading to a "ran out of registers" error.
To solve this, this introduces DAG mutator in the pre-scheduler with zero latency edge between such copies and such instructions, thus preventing the scheduler from creating the undesired interference.